COOK pasta as directed on package omitting salt; drain.
MEANWHILE, cook and stir chicken and onions in hot oil in large skillet on medium heat 5 to 7 min. or until onions are crisp-tender and chicken is done. Add pasta, broccoli, soup and milk; stir. Cover. Cook 6 to 8 min. or until heated through.
STIR in 1/2 cup cheese. Sprinkle with remaining cheese; cover. Cook 5 min. or until cheese is melted.